APOE and central nervous system cancer: CpG is efficiently loaded in apolipoprotein E peptide‐directed polymersomes to give blood‐brain barrier permeable and glioma and cervical lymph node‐homing CpG nano‐immunoadjuvant (t‐NanoCpG) which strongly stimulates the maturation of dendritic cells, antigen cross‐presentation, and production of proinflammatory cytokines in vivo.